Pick your way over the car-sized boulders in the wilds of Zuma Canyon outside Malibu.

Although it slices only six miles inland from the Pacific shoreline, Zuma Canyon harbors one of the deepest gorges in the Santa Monica Mountains -- and it has the further distinction of never having suffered the invasion of a major road. Under cover of junglelike growths of willow, sycamore, oak, and bay, the canyon's small stream cascades over sculpted sandstone boulders and gathers in limpid pools adorned with ferns. These natural treasures yield their secrets begrudgingly, as they should, only to those willing to scramble over boulders, plow through sucking mud and cattails, and thrash through scratchy undergrowth.

On this challenging-at-times trek, you'll proceed straight up the canyon's scenic midsection, climb out of the canyon depths via a power line service road, and loop back to your starting point on a ridge-running fire road. The roads are shadeless, yet they offer great vistas of the canyon, the ocean, and the east-west sweep of the Santa Monica Mountains.

Note that winter flooding can render narrow parts of the canyon impassable, but such episodes are uncommon and short-lived. During spring, the stream flows heartily and there's plenty of greenery and wildflowers -- plus more chance of exposure to poison oak and encounters with rattlesnakes.

A good starting place is the north end of Busch Drive, one mile from Pacific Coast Highway in the Point Dume area of Malibu. The fire road on your left, the Zuma Ridge Trail, is your return route. Take the path across the hillside to your right (east). You lose about 300 feet of elevation as you zigzag down to the wide flood plain issuing from the mouth of Zuma Canyon.

Cross Zuma Canyon's creek, and turn left on the path going upstream. You'll pass statuesque sycamores, tall laurel sumac bushes, and scattered wildflowers in season. After about a mile's walk, the canyon walls close in tighter, oaks appear in greater numbers, and you'll notice a small grove of eucalyptus trees on a little terrace. A short while later, the path abruptly ends at a pile of sandstone boulders. Now you begin a nearly two-mile stretch of boulder-hopping (and possibly wading); two or three hours' worth, depending on the conditions.

The great variety of rocks that have been washed down the stream or have fallen from the canyon walls says a lot about the geologic complexity of the Santa Monicas. You'll scramble over fine-grained siltstones and sandstones, conglomerates that look like poorly mixed aggregate concrete, and colorful volcanic rocks. Some of the larger boulders attain the dimensions of midsized trucks, presenting an obstacle course that must be negotiated by moderate hand-and-foot climbing.

About 0.5 mile shy of the Edison service-road crossing, you'll pass directly under a set of high-voltage transmission lines -- so high they're hard to spot. When you finally reach the Edison Road, turn left and follow it to the top of the west ridge. From there, turn left on the Zuma Ridge Trail and follow its lazily curving, downhill course back to the starting point. This and other dirt roads in the Santa Monicas that are closed to motorized vehicles are popular among mountain bikers as well as hikers.

This article contains information about a publicly owned recreation or wilderness area. Trails and pathways are not necessarily marked. Conditions can change rapidly. Hikers should be properly equipped and have safety and navigational skills. The Reader and Jerry Schad assume no responsibility for any adverse experience.